N-(carboxyphenyl) trimellitimide derivatives



United States Patent C N-(CARBOXYPHENYD rrrrnnna namvarrvw Richard E. Van Strien, Griffith, Ind, and James R.

This invention relates to novel aromatic dica-rboxylic acids having an internal imide group and polyester-imides prepared therefrom, and more particularly to novel aromatic dicarboxylic acids of the formula:

Q n COOH N COOH COOH

when reacted with a saturated dihydric alcohol, particularly one having from about 2 to 4 carbon atoms, produces .a polyester-imide which as a coating or fiber exhibits highly desirable properties at elevated temperatures.

In order to clearly locate the position of each carboxyl group in the aromatic dicarboxylic acid, .the formula for the dicarboxylic acid may be represented by:

It is understood that the carboxyl group on each of the aromatic groups may be in any one of the open positions. However, it is preferred that at least one is in the par-a position and especially preferred that both are in the para position resulting in N-(pcarboxyphenyl) trimel-litimide.

The aromatic dicarboxylic acid is reacted with a dihydric alcohol to produce the polyester-irnide. Normal-1y, the alcohol is saturated and preferably has from 2 to about 4 carbon atoms since these are so readily available and have been utilized advantageously in the past for polyester products. Desirable alcohols include ethylene glycol, propylene glycol, butylene glycol, diethylene glycol and the like. Ethylene glycol is preferred because of the desirable polymers produced from it.

3,217,014 Patented Nov. 9, 1965 The product of the aromatic dicarboxylic acid and dihydric alcohol is a polyester-imide made up substantially of the following units:

where n is greater than 1 and R is the residue from the dihy-dric alcohol, preferably a saturated di-hydric alcohol.

Naturally, the position of the carboalkoxy groups on the acidic residue in the polyester-imi-de depends on the particular dicarboxylic acid employed. It is preferred that at least one of the carboalkoxy groups be in the para position with respect to the carbons attached to the internal imide, and especially preferred that both are in the para or 4(4') position for particularly desirable high temperature properties in the polymer.

The aromatic dica-rboxy-lic acid is prepared by condensirig a benzene trioarboxylic acid anhydride or its acid with aminobenzoic acid. Suitable reactants include trimellitic anhydride, trimellitic acid, hemimellitic anhydride, and the like; and ortho, metal or para aminobenzoic acid. Naturally mixtures of these reactants may also be employed. The reactants may be substituted or unsubstituted. The desired substituents do not enter int-o the condensation reaction. The process for preparing the arcmatic dicarboxylic acid comprises reacting the benzene tricarboxylic acid anhydride and aminobenzoic acid at an elevated temperature for a sufficient time to produce the dicarboxylic acid. Typically, with trimellitic anhydride and p-arninobenzoic acid, the reaction proceeds at a temperature in the order of 270 F. although somewhat lower temperatures are also suitable. The time suflicient to produce the dicarboxylic acid is in the order of 2 /2 hours when the temperature is gradually raised up to 270 F. Suitable solvents such as dimethylforrnamide are generally employed. Naturally, when the acid (trirnellitic acid) is utilized, greater condensation conditions are required.

When such solvents as dimethylformamide are present, the p,-p-aromatic dicarboxylic acid precipitates out of the solution. It is then normally washed with water and filtered. Other of the acids may be recovered in the same or similar manner.

The polyester-imide is prepared in the polycondensation reaction of the aromatic dicarboxylic acid and the defined dihydric alcohol. Typically, for N-(p-carboxylphenyl) trimel-litimide and ethylene glycol, the reactants are first heated by an ethylene glycol vapor bath, after which small amounts of catalyst such as zinc acetate and antimony trioxide are added. Vacuum is then usually applied and the heating continued for periods of time in the order of 2 hours. A dimethylphthalate vapor bath is usually then employed to remove unreacted ethylene glycol and the heating continued for approximately 1 hour. During this procedure, the polymer solidifies. It is then cooled. When particular polymers, surface coatings, or fibers are desired, these procedures may be modified by techniques normally utilized for the particular product by those skilled in the art.

The defined aromatic dicarboxylic acid may be used in conjunction with other acids such as terephthalic acid in preparing polyester-irnides. In addition to its benefits afforded the polymers at higher temperatures, it offers advantages for fibers which are dyed. The following examples illustrate some embodiments of this invention. These are intended for illustrative purposes only and not intended to limit the scope of the invention.

3 Example I Approximately 6.0 moles (1,152 gm.) of trimellitic anhydride, 60 moles (822 gm.) of p-aminobenzoic acid, and 3,000 ml. of dimethylformamide were charged to a reaction flask. A mild exothermic reaction was noted. Heat was then applied during which the contents were stirred. The reaction temperature was gradually raised until it reached approximately 270 F; after approximately 2 /2 hours of heating. A precipitate then formed, making stirring impossible. Approximately 3,000 ml. of additional DMF were added to the contents of the flask for easier handling. The product was then added to four volumes of water and was then filtered. The crude, dried product was light yellow and weighed approximately 1,500 gm. The color was improved by washing with glacial acetic acid. An acid number 540 (mg. KOI-I/gm.) was determined which checked with the theoretical value of 540 (for a tricarboxylic acid). The product was N-(pcarboxyphenyl) trimellitimide.

Example 11 A polyester-imide was prepared from the dicarboxylic acid (15.6 gm.) of Example I and ethylene glycol (9.5 gm.) As indicated from these amounts, an excess of the glycol was utilized. The reactants were charged to a glass polyesterification apparatus which was equipped with facilities for operating with vacuum and stirring. The latter was made from glass capillary tubing which provided a means to sparge the polymer with nitrogen.

After being swept with nitrogen, the reactants were heated for approximately one hour by an ethylene glycol vapor bath. Then 0.01 gm. each of Zinc acetate and antimony trioxide were added. Next vacuum was slowly applied and the heating was continued for approximately two additional hours during which the acid dissolved.

The ethylene glycol vapor bath was then replaced with a tially above the melting temperature of 256 C. characteristic of polyesters from terephthalic acid and ethylene glycol.

The above disclosure reveals that applicants have provided an aromatic dicarboxylic and polyester-imide which exhibit many features desirable for commercial products. Thus, having described the invention, what is claimed is: 1. An aromatic dicarboxylic acid of the formula:

ll 1 2 3 H000 C\N 1 4 f a 5' c0011 0 2. The acid of claim 1 wherein the COOH is on the 4' position.

3. N-(p-carboxyphenyl) trimellitimide.

References Cited by the Examiner UNITED STATES PATENTS 2,556,664 6/51 Smith et al 260326 2,997,462 8/61 Wulfi et al. 26075 3,051,724 8/62 Bolton et al. 260326 3,060,152 10/62 Ringwald 26075 3,060,191 10/62 Kolb et al 260326 3,078,228 2/63 Smith et al 260326 3,122,559 2/64 Bolton et al. 260326 NICHOLAS S. RIZZO, Primary Examiner. 

1. AN AROMATIC DICARBOXYLIC ACID OF THE FORMULA: 